Polarity switching method in consumable electrode AC pulse arc welding

Abstract

A polarity switching control method is provided for consumable electrode AC pulse arc welding. By the method, a peak current and a base current are applied during an electrode-positive polarity period, while an electrode-negative current is applied during an electrode-negative polarity period. For performing the welding, polarity switching is performed to alternate the electrode-positive polarity period and the electrode-negative polarity period. When a consumable electrode and a base metal are in short circuit with each other, the polarity switching is performed after the short circuit is broken and an arc is generated.

The invention claimed is: 
     
       1. A polarity switching control method in consumable electrode AC pulse arc welding under power supply from a welding power source, the method comprising:
 applying a peak current and a base current during an electrode-positive polarity period; 
 applying an electrode-negative current during an electrode-negative polarity period; and 
 conducting polarity switching between the electrode-positive polarity period and the electrode-negative polarity period in response to a temporary operation-stop signal for temporarily stopping the power supply from the welding power source, the temporary operation-stop signal being output following output of a pulse period signal that causes an average of variable welding voltage to be equal to a voltage setting; 
 conducting the polarity switching from positive to negative after a predetermined delay period has lapsed in response to the temporary operation-stop signal that is also delayed from the pulse period signal by at least said predetermined delay period, when a single consumable electrode and a base metal come in short circuit with each other during the electrode-positive polarity period, said predetermined delay period being provided for the single consumable electrode; and 
 conducting the polarity switching from positive to negative in response to the temporary power-stop signal that is not delayed from the pulse period signal, when the consumable electrode and the base metal do not come in short circuit with each other during the electrode-positive polarity period. 
 
     
     
       2. The method according to  claim 1 , wherein a welding current applied at the generation of the arc is maintained during the delay period.